How to Customize and Deploy your Salesforce Login Page?

After creating your salesforce subdomain. You can create a login page of your own. You can customize your login page so that user need not look at a URL to recognize your site.

What can you customize in the login page?

1. You can add brand or company logo on the login page.
2. You can change the background color.
3. You can replace the right side of login page with some message or picture.

Steps to customize login page :

1. 1. Go to setup and enter my domain in the quick find box and select myDomain.

1. Right to ‘Authentication Configuration’ click edit.
   
2. A form will open, From the choose file, upload an image for your brand logo. It will be displayed at the top left of the login page.
   
3. Right to ‘Background Color’ header enter the hexadecimal color code or click the color picker in the text box to change the background color of your login page.
4. Mark the checkbox for ‘Use the native browser for user authentication on iOS’ to true if you want to redirect users for salesforce1 and mobile SDK applications on IOS devices to their native browser when using single sign-on authentication into your custom domain
5. Mark the checkbox for ‘Use the native browser for user authentication on Android’ to true if you want to redirect users for salesforce1 and mobile SDK applications on Android devices to their native browser when using single sign-on authentication into your custom domain.
6. Right to ‘Right Frame URL’ header enter the URL of the file that’s hosted at a URL using SSL encryption and has the https:// prefix in the textbox. This file will be displayed on the right side of the login page.
7. Click save.
8. Logout of your org and see the new login page for your Org.your new login page look like below screenshot :
   

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Reference:
https://trailhead.salesforce.com/en/projects/quickstart-lightning-components/steps/quickstart-lightning-components1